Question 148587
Slope-intercept form
{{{y=mx+b}}}
Slope of horizontal line is 0. 
{{{y=mx+b}}}
{{{y=0*x+b}}}
{{{y=b}}}
Use your point (-5,-7):
{{{y=b}}}
{{{-7=b}}}
{{{b=-7}}}
Your equation is therefore,
{{{y=-7}}}